| David Brownell | d29389d | 2009-01-06 14:41:41 -0800 | [diff] [blame] | 1 | #ifndef __LINUX_SPI_GPIO_H |
| 2 | #define __LINUX_SPI_GPIO_H |
| 3 | |
| 4 | /* |
| 5 | * For each bitbanged SPI bus, set up a platform_device node with: |
| 6 | * - name "spi_gpio" |
| 7 | * - id the same as the SPI bus number it implements |
| 8 | * - dev.platform data pointing to a struct spi_gpio_platform_data |
| 9 | * |
| 10 | * Or, see the driver code for information about speedups that are |
| 11 | * possible on platforms that support inlined access for GPIOs (no |
| 12 | * spi_gpio_platform_data is used). |
| 13 | * |
| 14 | * Use spi_board_info with these busses in the usual way, being sure |
| 15 | * that the controller_data being the GPIO used for each device's |
| 16 | * chipselect: |
| 17 | * |
| 18 | * static struct spi_board_info ... [] = { |
| 19 | * ... |
| 20 | * // this slave uses GPIO 42 for its chipselect |
| 21 | * .controller_data = (void *) 42, |
| 22 | * ... |
| 23 | * // this one uses GPIO 86 for its chipselect |
| 24 | * .controller_data = (void *) 86, |
| 25 | * ... |
| 26 | * }; |
| 27 | * |
| 28 | * If the bitbanged bus is later switched to a "native" controller, |
| 29 | * that platform_device and controller_data should be removed. |
| 30 | */ |
| 31 | |
| 32 | /** |
| 33 | * struct spi_gpio_platform_data - parameter for bitbanged SPI master |
| 34 | * @sck: number of the GPIO used for clock output |
| 35 | * @mosi: number of the GPIO used for Master Output, Slave In (MOSI) data |
| 36 | * @miso: number of the GPIO used for Master Input, Slave Output (MISO) data |
| 37 | * @num_chipselect: how many slaves to allow |
| 38 | * |
| 39 | * All GPIO signals used with the SPI bus managed through this driver |
| 40 | * (chipselects, MOSI, MISO, SCK) must be configured as GPIOs, instead |
| 41 | * of some alternate function. |
| 42 | * |
| 43 | * It can be convenient to use this driver with pins that have alternate |
| 44 | * functions associated with a "native" SPI controller if a driver for that |
| 45 | * controller is not available, or is missing important functionality. |
| 46 | * |
| 47 | * On platforms which can do so, configure MISO with a weak pullup unless |
| 48 | * there's an external pullup on that signal. That saves power by avoiding |
| 49 | * floating signals. (A weak pulldown would save power too, but many |
| 50 | * drivers expect to see all-ones data as the no slave "response".) |
| 51 | */ |
| 52 | struct spi_gpio_platform_data { |
| 53 | unsigned sck; |
| 54 | unsigned mosi; |
| 55 | unsigned miso; |
| 56 | |
| 57 | u16 num_chipselect; |
| 58 | }; |
| 59 | |
| 60 | #endif /* __LINUX_SPI_GPIO_H */ |